This invention relates to lamps and, in particular, to a lamp and socket assembly providing repeatable mechanical alignment of the lamp and reliable electrical contact with the lamp.
In the past, a number of lamps used as signal lamps, e.g. for automobiles, comprised a brass base having pins for securing the base to the socket. As known in the art, the lamp can move slightly in its socket, making repeatable positioning of the filament difficult and allowing the lamp to change position due to vibration or shock. In addition, since the base is not sealed from dirt and moisture, the base may corrode and fuse to the socket causing poor electrical contact in service and breakage when the lamp is removed.
While "prefocused" lamps are available, in which the base contains a flange for mounting the lamp and from which the filament is accurately located, it is also desirable to reduce the number of types of bases. For example, it is desirable to have a single base and socket assembly which can be used for either front or rear insertion and which has the "prefocused" characteristic.
Prior attempts to solve these problems, for example, as described in U.S. Pat. Nos. 3,749,960 and 3,999,095, have not proven entirely satisfactory. In the former, the base of the lamp is mechanically secured to the panel or reflector by a locking ring or gasket while a connector attaches to the base of the lamp and electrically connects with pins protruding therefrom. Thus, replacement of the lamp is difficult due to the gasket. The separate gasket also adds to the parts count and cost. Further, the lamp and base are physically long which may be undesirable, e.g., in the trunk of a car.
The latter patent describes a lamp and socket having a shorter overall length. However, the lamp is mechanically connected to the electrical connector which, in turn, is mechanically connected to a panel or reflector by way of a resilient gasket. This indirect mechanical connection of the lamp to the reference (panel or reflector) particularly when combined with the resilient gasket can lead to errors in the positioning of the bulb. A partial solution is to manufacture the rigid parts to very tight tolerances so that cumulative errors do not exceed a predetermined tolerance. Even if this were done, the gasket remains a source of positioning error.